With the constantly improving quality of color photocopies and printings and in an attempt to protect high value documents and high value articles such as banknotes, identity documents and high value goods, it has been the conventional practice to incorporate various security elements in or on these documents or articles. Typical examples of security elements include security threads or stripes, windows, fibers, planchettes, foils, decals, holograms, watermarks, security inks or compositions comprising optically variable pigment particles, magnetic or magnetizable optically variable pigment particles, thermochromic pigment particles, photochromic pigment particles, luminescent, infrared-absorbing, ultraviolet-absorbing or magnetic compounds.
Nowadays, counterfeiting is a global problem which has an impact not only on manufacturers but also on the consumers and governments. Indeed, counterfeiting may also have an impact on government revenues in that it affects the collection of taxes for example for cigarettes and alcohols because of the existence of a black market where it is impossible to track and trace counterfeit (smuggled, diverted, etc.) products with no valid tax stamps.
Various solutions have been developed in the field of packaging or as a protection for items or goods and mainly used for high value documents or high value articles. Those solutions include the incorporation of tamper evident structures or void tamper security evident structures which include a proof of any alteration or manipulation of packaging or items or good that may have occurred.
For example, labels or items whose primary function is the security and prevention of counterfeiting or illegal reproduction of high value articles may be forcibly removed or detached with the fraudulent aim of re-using them on articles of lesser value. Typical examples of such fraudulent activities include the increase of temperature to be able to remove the labels or items intact and thereby allowing their re-use on other less valuable or fake articles. The need for security and for identification of any tampering that might have occurred involves many and diversified fields including without limitation the food and wine industry, the cosmetic industry, the pharmaceutical industry, the food processing industry, the electrical/electronic industry, tax stamps or banderols. To overcome those fraudulent activities, various solutions have been developed and include for example the incorporation of tamper evident structures or void tamper security evident structures which include a proof of any alteration or manipulation that may have occurred.
For example, temperature-indicating materials capable of changing their color tone upon exposure to a defined temperature have been used as means for detecting whether a particular product experienced or was exposed to a temperature exceeding a predetermined level or not. Examples of known temperature-indicating materials include heat-fusible substances and acid-base indicators, the temperature-indicating materials being reversible temperature indicators since they undergo color change upon heating and the color tone thereof returns back to the original one when they are cooled.
US 2013/0014690, which is incorporated by reference herein in its entirety, discloses a temperature management indicator which is capable of indicating specific temperature ranges by reversible color changes. The disclosed temperature management indicator comprises a reversible temperature indicating member including reversible temperature indicating pigment particles devoid of mercury, the pigment particles being dispersed in a resin. It is further disclosed that an additional irreversible temperature indicating member may be arranged on an indicator base plate, the irreversible temperature indicating member including a thermofusible substance-absorptive base material or a thermofusible substance-permeable material.
US 2001/0044014, which is incorporated by reference herein in its entirety, discloses an irreversible heat-sensitive composition comprising a mixture of a granular or powdery heat-fusible substance having a melting point corresponding to a temperature to be recorded and a granular or powdery dyestuff diffusible into the fused heat-fusible substance through dispersion or dissolution. A heat-sensitive indicator comprising a substrate provided thereon with the printed heat-sensitive ink is further disclosed.
Therefore, there remains a need for a solution combining high security against counterfeiting and illegal reproduction as well as avoiding fake, manipulation, alteration or diversion of goods, articles, items or packaging containing any valuable products.